Cook “Confirms” 97 Percent Consensus

Opinions about whether or not humans cause climate change depend on the expertise of those giving them, according to research. The latest paper from John Cook of the University of Queensland revisits his previous research and appears to confirm that there is a consensus among 97 percent of climate experts that humans cause global warming. This graphic appears in the paper and illustrates the level of consensus on AGW versus expertise across different studies. Courtesy: authors and Environmental Research Letters.

Expertise matters in opinions over human-caused climate change, according to the latest paper from John Cook and colleagues which revisits his previous research to confirm a consensus among 97 percent of climate experts that humans cause global warming.

By Allison Mills, Michigan Tech

A research team confirms that 97 percent of climate scientists agree that climate change is caused by humans. The group includes Sarah Green, a chemistry professor at Michigan Technological University.

“What’s important is that this is not just one study—it’s the consensus of multiple studies,” Green says. This consistency across studies contrasts with the language used by climate change doubters. This perspective stems from, as the authors write, “conflating the opinions of non-experts with experts and assuming that lack of affirmation equals dissent.”

Environmental Research Letters published the paper this week. In it, the team lays out what they call “consensus on consensus” and draws from seven independent consensus studies by the co-authors. This includes a study from 2013, in which the researchers surveyed more than 11,000 abstracts and found most scientists agree that humans are causing climate change. Through this new collaboration, multiple consensus researchers—and their data gathered from different approaches—lead to essentially the same conclusion.

The key factor comes down to expertise: The more expertise in climate science the scientists have, the more they agree on human-caused climate change.

Skeptic vs. Doubter

There are many surveys about climate change consensus. The problem with some surveys, Green points out, is that they are biased towards populations with predetermined points of view. Additionally, respondents to some surveys lack scientific expertise in climate science.

“The public has a very skewed view of how much disagreement there is in the scientific community,” she says. Only 12 percent of the US public are aware there is such strong scientific agreement in this area, and those who reject mainstream climate science continue to claim that there is a lack of scientific consensus. People who think scientists are still debating climate change do not see the problem as urgent and are unlikely to support solutions.

This new paper is a rebuttal to a comment criticizing the 2013 paper. Green is quick to point out that skepticism, a drive to dig deeper and seeking to better validate data, is a crucial part of the scientific process.

“But climate change denial is not about scientific skepticism,” she says.

Broader Impacts

Refuting climate change doubters is the main purpose of a website Green contributes to called skepticalscience.com. The website is run by the new study’s lead author, John Cook from the University of Queensland in Australia. He says consensus studies have helped change political dialogue around climate change.

“The progress made at the United Nations Climate Change Conference (COP21) in Paris late last year indicates that countries are now well and truly behind the scientific consensus, too,” Cook says.

Co-author Naomi Oreskes from Harvard University originally pursued consensus data about climate change in 2004 and co-wrote Merchants of Doubt, which was turned into a documentary in 2014. She says that this latest work places the findings in the broader context of other research.

“By compiling and analyzing all of this research—essentially a meta-study of meta-studies—we’ve established a consistent picture with high levels of scientific agreement among climate experts,” she says.

And among climate scientists, there’s little doubt. There is consensus on consensus.

Abstract

The consensus that humans are causing recent global warming is shared by 90%–100% of publishing climate scientists according to six independent studies by co-authors of this paper. Those results are consistent with the 97% consensus reported by Cook et al (Environ. Res. Lett. 8 024024) based on 11 944 abstracts of research papers, of which 4014 took a position on the cause of recent global warming. A survey of authors of those papers (N = 2412 papers) also supported a 97% consensus. Tol (2016 Environ. Res. Lett.11 048001) comes to a different conclusion using results from surveys of non-experts such as economic geologists and a self-selected group of those who reject the consensus. We demonstrate that this outcome is not unexpected because the level of consensus correlates with expertise in climate science. At one point, Tol also reduces the apparent consensus by assuming that abstracts that do not explicitly state the cause of global warming (‘no position’) represent non-endorsement, an approach that if applied elsewhere would reject consensus on well-established theories such as plate tectonics. We examine the available studies and conclude that the finding of 97% consensus in published climate research is robust and consistent with other surveys of climate scientists and peer-reviewed studies.